As a typical oxide superconductor having a superconducting transition temperature Tc higher than the boiling point of liquid nitrogen, a perovskite RBa.sub.2 Cu.sub.3 O.sub.7 of three-layered structure, in which R is one or more of elements selected from the group consisting of Y and lanthanide series rare earth element has been known. Further, a RBa.sub.2 Cu.sub.4 O.sub.8 type oxide in which a Cu-O single bond in the RBa.sub.2 Cu.sub.3 O.sub.7 type oxide is changed into a double bond structure has also been known as a superconductor having Tc higher than of the boiling point of liquid nitrogen.
By the way, for the method of manufacturing the oxide superconductor described above into a thin film, the following two methods are generally adopted.
(1) A method of vapor depositing a starting metallic material by applying a deposition process such as laser deposition, active reaction deposition, sputtering or like other method, while locally blowing a gas such as oxygen in a film-forming chamber undergoing vapor deposition, forming an amorphous oxide of an appropriate composition into a thin film or crystallizing the oxide superconductor.
(2) A method of evacuating the inside of the film-forming chamber to a vacuum degree of about 1.times.10.sup.-7 Torr, then evaporating metals such as Y and Cu, and BaF.sub.2 on a substrate from an electron impinging type vapor deposition source and then oxidizing and crystallizing the superconducting material by applying a subsequent heat treatment in an oxygen atmosphere (disclosed, for example, by R. Feenstra, et al., in J. Appl. Phys. (Submitted)).
However, each of the prior arts as described above have the following respective drawbacks.
At first, in the method (1), it is difficult to form a thin superconductor film at high quality over a region of a large area of greater than 100 cm.sup.2 in view of the constitution of the film-forming device, the difficulty in uniform supply of activating oxygen or the like. In addition, since the gas such as oxygen is introduced at the same time with film formation, the surface of the starting metallic material is oxidized, making evaporation instable and making it difficult for the accurate control of the film-forming rate and the film composition. On the other hand, in the method (2) above, film formation to a region of a large area can be conducted relatively easily since there is less restriction in view of the constitution of the device. However, this method inevitably suffers from intrusion of impurities upon vapor deposition due to residual gases such as H.sub.2 O, N.sub.2, H.sub.2 and CO.sub.2. Further, since BaF.sub.2 is used as an evaporation source, it is necessary to remove a F-content in the film upon oxidation and crystallization by reaction with steams at a high temperature in addition to reaction with oxygen. As a result, this not only makes the operation complicate but also generates a toxic HF gas of highly corrosive nature during reaction to bring about a problem in view of safety and sanitation. Further, since the evaporation state of BaF.sub.2 is instable, it is difficult for the accurate control of the film composition.
The present invention has been achieved in order to overcome the technical problems involved in the prior art and it is an object thereof to provide a method of manufacturing an oxide superconductor film capable of easily controlling a film-forming rate and a film composition, producing the film safely and economically over a wide region, homogeneously and at a high quality.